The present invention relates to a semiconductor device and method of manufacture thereof, a circuit board and an electronic instrument.
In the well-known semiconductor device package form T-BGA (Tape Ball Grid Array), or CSP of the fan-out type or fan-in/out type, the package size is slightly larger than the chip size. In a semiconductor device of this form, a flexible substrate is used, and on the part of the flexible substrate protrucing from the semiconductor chip also, solder balls are provided. Then to ensure the coplanarity of the solder balls, a stiffener is commonly adhered.
However, bearing in mind the stiffness, workability, and other factors, stainless steel is used for the stiffener, and this is not only expensive, but also requires separate procurement of the component only when necessary.
The present invention solves these problems, and has as its objective the provision of a semiconductor device and method of manufacture thereof, a circuit board and an electronic instrument, such that an expensive stiffener can be omitted and coplanarity can be assured by using the components used in the mounting process.
(1) The semiconductor device according to one aspect of the present invention comprises:
a semiconductor chip on which a plurality of electrodes are formed;
a first flexible substrate on which a wiring pattern is formed and on which the semiconductor chip is mounted;
a plurality of external terminals electrically connected to the electrodes with the wiring pattern interposed; and
a second flexible substrate adhered to the first flexible substrate avoiding the semiconductor chip.
According to this aspect of the present invention, since the first flexible substrate is larger than the semiconductor chip, a part projects outside the semiconductor chip, and the second flexible substrate is adhered to this part. By means of this, the first flexible substrate is strengthened, and the coplanarity of the external terminals is assured. Since the component used for strengthening is also a flexible substrate, no expensive stiffener is required.
(2) In this semiconductor device, the first and second flexible substrates may be of the same material and of substantially the same thickness.
Since a single type of component is used the cost can be reduced.
(3) In this semiconductor device, the wiring pattern may be disposed to face the second flexible substrate; a plurality of through holes may be formed in the first flexible substrate; the external terminals nay be provided to be connected with the wiring pattern via the through holes; and the external terminals may project from a surface of the first flexible substrate opposite to that on which the wiring pattern is formed.
Since the wiring pattern is positioned between the first and second flexible substrates, both sides of the wiring pattern can be covered and protected.
(4) The semiconductor device may further comprise a conductive layer which is formed between the first and second flexible substrates, of the same material and of substantially the same thickness as the wiring pattern, and is electrically insulated from the wiring pattern.
Since a pair of electrically conductive components of~the same material and the same thickness is provided between the first and second flexible substrates, the construction is symmetrical in the thickness direction.
(5) In this semiconductor device, the means of adherence of the first flexible substrate and the wiring pattern, and the means of adherence of the second flexible substrate and the conductive layer may he the same.
By means of this, after consideration of the means of adherence, the construction is symmetrical in the thickness direction.
(6) In this semiconductor device, the conductive layer may be of a symmetrical form with the wiring pattern.
By means of this, the construction is symmetrical not only in the thickness direction but also in the plane.
(7) In this semiconductor device, a first insulating film may be formed on a surface of the wiring pattern opposite to the first flexible substrate; and a second insulating film may be formed on a surface of the conductive layer opposite to the second flexible substrate.
Electrical insulation of the wiring pattern and the conductive layer can be achieved by the first and second insulating films.
(8) In this semiconductor device, the electrodes of the semiconductor chip may be electrically connected to the wiring pattern by an anisotropic conductive material having electrically conductive particles dispersed in an adhesive; and the first and second flexible substrates may be adhered to each other by the anisotropic conductive material.
Since the component electrically connecting the electrodes of the semiconductor chip to the wiring pattern is the component for adhesion of the first and second flexible substrates, the number of components can be reduced, and the cost can be reduced.
(9) In this semiconductor device, the first and second flexible substrates may be adhered to each other by a resin; and the resin may be provided on a surface of the first flexible substrate on which the wiring pattern is formed, and be in close contact with a surface of the wiring pattern facing the second flexible substrate and edge surfaces of the wiring pattern.
By means of this, the resin adhering the first and second flexible substrates is in close contact with the wiring pattern. So that gaps allowing moisture to accumulate are eliminated from the surface of the wiring pattern, and the moisture resistance is improved.
(10) On a circuit board of the present invention is mounted the above mentioned semiconductor device.
(11) An electronic instrument of the present invention has the above mentioned semiconductor device.
(12) A method of manufacture of a semiconductor device according to another aspect of the present invention comprises the steps of:
providing a semiconductor chip which has a plurality of electrodes, a first flexible substrate on which a wiring pattern is formed, and a second flexible substrate;
mounting the semiconductor chip on the first flexible substrate;
adhering the second flexible substrate to a portion of the first flexible substrate avoiding a region in which the semiconductor chip is mounted; and
providing external terminals electrically connected to the electrodes with the wiring pattern interposed.
According to this aspect of the present invention, since the first flexible substrate is larger than the semiconductor chip, a part projects outside the semiconductor chip, and the second flexible substrate is adhered to this part. By means of this, the first flexible substrate is strengthened, and the coplanarity of the external terminals is assured. Since the component used for strengthening is also a flexible substrate, no expensive stiffener is required.
(13) The method of manufacture of a semiconductor device may further comprise a step of punching out the first and second flexible substrates after the step in which the second flexible substrate is adhered.
By means of this, the first and second flexible substrates are punched out, and the final form of the semiconductor device can be obtained.
(14) In this method of manufacture of a semiconductor device, the first and second flexible substrates may be in tape form; the wiring pattern may be repeatedly formed on the first flexible substrate; and a hole may be formed repeatedly on the second flexible substrate to avoid the semiconductor chip.
By means of this, a plurality of semiconductor devices can be manufactured continuously.
(15) The method of manufacture of a semiconductor device may further comprise a step of punching out the first flexible substrate avoiding the second flexible substrate after the step in which the second flexible substrate is adhered.
Since only the first flexible substrate is punched out, compared with the case in which the first and second flexible substrates are punched out, the processing is simplified, and the blanking die can be made inexpensive and of long life.
(16) In this method of manufacture of a semiconductor device, the first flexible substrate may be in tape form; the second flexible substrate may be formed to be smaller than a region punched out in the first flexible substrate; the wiring pattern may be formed repeatedly on the first flexible substrate; and a hole may be formed in the second flexible substrate so as to avoid the semiconductor chip.
Since the first flexible substrate is in tape form, a plurality of semiconductor devices can be manufactured continuously.
(17) In this method of manufacture of a semiconductor device, the step of mounting the semiconductor chip may be carried out after the step of adhering the second flexible substrate.
(18) In this method of manufacture of a semiconductor m device, the step of adhering the second flexible substrate may be carried out after the step of mounting the semiconductor chip.
(19) In this method of manufacture of a semiconductor device, the step of mounting the semiconductor chip may include a step of providing an anisotropic conductive material having electrically conductive particles dispersed in an adhesive on the first flexible substrate, exceeding a region of mounting the semiconductor chip, and a step of electrically connecting the electrodes to the wiring pattern with the anisotropic conductive material interposed and the second flexible substrate may be adhered to the first flexible substrate by the anisotropic conductive material in the step of adhering the second flexible substrate.
Since the first and second flexible substrates are adhered by using the material which electrically connects the electrodes of the semiconductor chip to the wiring pattern, the number of steps of applying material for adhesion can be reduced.
(20) In this method of manufacture of a semiconductor device, the step of adhering the second flexible substrate may include: a step in which a resin is applied to at least one of the first and second flexible substrates; and a step in which the first and second flexible substrates are brought into close contact with the resin interposed to bring the resin into close contact with a surface of the wiring pattern facing the second flexible substrate and edge surfaces of the wiring pattern.
By means of this, the first and second flexible substrates are adhered by the resin, and the resin is brought into close contact with the wiring pattern. By means of this, gaps allowing moisture to accumulate are eliminated from the surface of the wiring pattern, and the moisture resistance is improved.
(21) In this method of manufacture of a semiconductor device, positioning holes may be formed in one of the first and second flexible substrates, and positioning marks may be formed in the other, and the holes and the marks may be aligned for positioning the first and second flexible substrates.
By means of this, the first and second flexible substrates can be provided in accurate positions.
(22) In this method of manufacture of a semiconductor device, the second flexible substrate may be formed of the same material and of the same thickness as the first flexible substrate.
Since a single type of component is used, the cost can be reduced.
(23) In this method of manufacture of a semiconductor device, a conductive layer of the same material and of the same thickness as the wiring pattern may be formed on the second flexible substrate; and the conductive layer and the wiring pattern may be disposed to face to each other and be made electrically insulated from each other; and the second flexible substrate may be adhered to the first flexible substrate.
By means of this, the first flexible substrate on which the wiring pattern is formed, and the second flexible substrate on which the conductive layer is formed are adhered. Since a pair of electrically conductive components of the same material and the same thickness is provided between the first and second flexible substrates, the construction is symmetrical in the thickness direction.
(24) In this method of manufacture of a semiconductor device, the conductive layer may be of a symmetrical form with the wiring pattern.
By means of this, the construction is symmetrical not only in the thickness direction but also in the plane.
(25) In this method of manufacture of a semiconductor device, a first insulating film is formed on the wiring pattern of the first flexible substrate; and a second insulating film is formed on the conductive layer of the second flexible substrate.
By means of this, electrical insulation of the wiring pattern and the conductive layer can be achieved by the first and second insulating films.